Field of the Disclosed Subject Matter
The disclosed subject matter relates to catheters used in the delivery of medical devices such as expandable members, self-expanding stents, and stents delivered by an expandable member for treating the luminal systems of a patient. Specifically, the disclosed subject matter relates to a delivery catheter having a retractable sheath moved by a hydraulic actuator.
Description of the Related Art
In general, catheters such as balloon catheters, can be used for a variety of suitable procedures and treatments. Such procedures include, but are not limited to, procedures for dilatation, delivery of medical devices such as stents, stent grafts, filters, and the like, and procedures for drug delivery. As known in the art, a variety of catheter devices treat the luminal system of a patient. Of such devices, many are directed to treating vascular systems, including both the cardiovascular system and the peripheral system of a patient. For example, the treatment of the cardiovascular system can include the performance of angioplasty or delivery of balloon-expandable or self-expanding interventional devices (e.g., stents). The treatment of the peripheral system includes treatment of the carotid, popliteal and renal vessels, among others.
The site of the occlusive lesion can often only be reached by a tortuous pathway through the vasculature of the patient. The difficulty in accessing such regions requires that the catheter must be sufficiently flexible longitudinally to follow the tortuous path to the desired site, and at the same time, sufficiently stiff axially to allow the distal end of the catheter to be pushed or otherwise manipulated from an external access location. In manipulating the catheter through the tortuous pathway, the catheter furthermore needs sufficient structure to maintain the patency of the balloon and/or any medical device delivered by the catheter, including preventing drugs or therapeutic agents from being released prematurely from the catheter prior to deployment.
A variety of systems using a retractable sheath are known for intraluminal delivery of a medical device, such as an expandable member, stent, stent graft, or filter. However, there remains a need for continued improvement of such known delivery systems.
An example of such a system is described in U.S. Pat. No. 6,425,898 to Wilson et al., which is incorporated by reference herein, wherein a delivery system is provided having an inner member with a stop attached to the inner member. During deployment, the stop prevents the stent from migrating proximally during retraction of the sheath for stent deployment.
Conventional medical device delivery systems generally comprise a handle portion and an elongated shaft, wherein a medical device such as an expandable member disposed at the distal end of the shaft. In certain embodiments, a retractable sheath can also be provided and initially disposed over the expandable member. To deploy the device, the outer sheath can be retracted relative to the expandable member, which can then be inflated to a deployed configuration. The sheath in such systems generally spans the full length of the catheter resulting in an increased profile and stiffness over the entire length of the catheter. Such stiffness and increased profile at the distal end of the catheter can restrict certain applications, such as neuro and other indications of particular size limitations. Further, because the sheath spans the full length of the catheter there is an increased risk of the sheath binding with other components of the catheter during passage through the tortuous luminal system of a patient, thus inhibiting the deployment of the stent.
Another issue with such delivery systems is that the sheath is generally pulled back in a 1-to-1 ratio with the user's input (force). Due to larger static friction forces, a large amount of initial input may be typically required to retract the sheath.
Further, the amount of force that is required to retract the sheath, particularly for balloons or stents of greater length as required for peripheral indications, can be substantial. To overcome this issue, a lubricious liner can be used to decrease the amount of force required to retract the sheath. However, there remains a need for an improved delivery system with a retractable sheath having reduced force requirements for delivery of the medical device.
There thus remains a continued need for an efficient and economic system for delivering a medical device that is easy to use and provides accurate placement. The presently disclosed subject matter satisfies these and other needs.